1. Field of the Invention
This invention relates to storage stable compositions derived from polyisocyanates and is more particularly concerned with storage stable aqueous solutions derived from polyisocyanates and with processes for their preparation and with uses thereof.
2. Description of the Prior Art
A variety of aqueous compositions derived from polyisocyanates is known in the art. Illustratively, aqueous emulsions, derived from polyisocyanates having all the isocyanate groups blocked by capping agents such as phenol, are described in U.S. Pat. Nos. 3,499,824; 3,933,677; 3,996,154 and 3,997,592. Water soluble solutions of the bisulfite complexes of blocked polyisocyanates and bisulfite-blocked isocyanate-terminated prepolymers are described in U.S. Pat. Nos. 3,483,189 and 3,984,365, respectively. Aqueous emulsions derived from solutions of polyisocyanates in dimethylformamide and like alkylated amides are described in U.S. Pat. No. 3,428,592.
U.S. Pat. No. 3,410,817 describes a polyurethane latex obtained by making an aqueous emulsion of an isocyanate-terminated prepolymer (optionally in the presence of a chain extender) and then precipitating the emulsion by addition of an alcohol.
U.S. Pat. No. 3,897,581 relates to the use of certain isocyanate-terminated prepolymers as water-curable adhesives for bonding of plywood and the like. Certain of the isocyanate-terminated prepolymers specifically described and exemplified are said to be soluble in water and to react therewith.
We have now found that novel homogeneous aqueous solutions, having prolonged stability on storage and having certain highly useful properties to be described hereafter, can be prepared in a manner not hitherto described.